I apologize in advance, to Bruce, if I am jumping the gun on this topic, but it is one that I have much interest in. And I hope that Bruce - if he cannot provide any real answers at this time - can take these questions under consideration for the future.

Under which conditions will it be possible to adapt Calidar to various RPG systems?
I know that Calidar is being created system-free to allow Bruce as much creative freedom as possible with no "restraints" imposed by the limitations of specific RPG systems. But I am absolutely sure that as soon as the first Calidar products are release, fans are going to start asking each other: 'How can I PLAY A GAME in Calidar?'

So, I was thinking about Bruce's options - and I'll admit I don't know enough about copyright law to figure out which is best for the setting and for Bruce (legally and financially). But here are my thoughts on options:

2. Bruce adopts something akin to the Open Game License (OGL)
The OGL allows Third Party Publishers (3PP) to produce RPG content within a legal framework that allows the use of somebody else's material without the original owner losing their copyright. When creating products, a 3PP must state which part of the product is Product Identity (PI) and cannot be used by others, and which part is Open Game Content (OGC) which others may adopt and build upon.
For example, this is what allows many 3PP to expand upon the Pathfinder rules without being sued by Paizo. The problem with this option is that Bruce is not producing a game system but a setting, so figuring out if the OGL even applies in such a situation is going to be tricky and confusing. But perhaps the method could work. It is difficult to see Bruce making any money from it - apart from perhaps more book sales because the setting now is supported by one or more game systems.

3. Bruce allows commercial use of Calidar on an individual license-basis
This is, in my mind, the most realistic and viable option. Game companies that want to use Calidar as a setting for whatever RPG system they have in mind, license the use from Bruce at a certain percentage of the sales, a yearly cost or something along those lines. The contract does not provide exclusivity and several companies may release competing products for the same or different RPG systems. The design strength of the production company will determine the success of sales and Bruce need not worry about putting all his eggs in one basket (different publishers, more RPG systems).
This is basically a variation of option 1 but provides would-be publishers with a realistic entry barrier to the market and has a greater chance of actually resulting in Calidar becoming a GAME world, as opposed to a world in fantasy fiction.

4. Bruce creates a community use-license
Bruce creates a community use-license similar to what Paizo has done. It allows for non-commercial use of certain design elements, meaning that fans can use Paizo's Pathfinder rules (and setting, I believe) when they create their own fan stuff and share it on forums, blogs etc.
Allowing fans to create and share content based on Calidar freely - under certain conditions - might be an option for Bruce, but we have to remember that it is perhaps easier for Paizo to set up such a system, because their game system is already based on OGC. Bruce may find it harder to set up a community use license that does not ruin his intellectual property rights / copy rights to the setting.
Allowing fans to freely create and distribute among themselves - non-profit - could spread knowledge of the setting, helping Bruce sell more books, but there is a risk that conversion to RPG systems becomes half-hearted and amateurish, killing interest.

5. Bruce says 'to Hell with it all'
Bruce decides to focus on his books and lets the Internet do what it always does anyway

I'd LOVE to get comments and ideas on this - from Bruce of course but also from the rest of the fans eagerly awaiting Calidar!

Spellweaver wrote:5. Bruce says 'to Hell with it all'
Bruce decides to focus on his books and lets the Internet do what it always does anyway

I'd LOVE to get comments and ideas on this - from Bruce of course but also from the rest of the fans eagerly awaiting Calidar!

Best option ever.

IMO, it's better off to let every GM do their own conversion, because they can use the system with which they -and their players- are more familiar. This way one GM can use Savage World, another GURPS another the (a)D&D edition of his choice, etc.

Spellweaver wrote:2. Bruce adopts something akin to the Open Game License (OGL)
The OGL allows Third Party Publishers (3PP) to produce RPG content within a legal framework that allows the use of somebody else's material without the original owner losing their copyright. When creating products, a 3PP must state which part of the product is Product Identity (PI) and cannot be used by others, and which part is Open Game Content (OGC) which others may adopt and build upon.
For example, this is what allows many 3PP to expand upon the Pathfinder rules without being sued by Paizo. The problem with this option is that Bruce is not producing a game system but a setting, so figuring out if the OGL even applies in such a situation is going to be tricky and confusing. But perhaps the method could work. It is difficult to see Bruce making any money from it - apart from perhaps more book sales because the setting now is supported by one or more game systems.

My guess that if/when there is a Kickstarter/IndeGoGo project for Calidar, stuff like full-blown roleplaying products would be a stretch goal. The main target would probably be to get World of Calidar up and running and get the stories and art and stuff like that made and turn it into something that is self-financing. But if there was a ton of extra money that came in, that would obviously allow Bruce to fund things that he didn't have in his original plan.

I personally play with 3rd Edition D&D rules (and could probably get by with a Pathfinder conversion of Calidar) but I think that a conversion of Calidar to Dark Dungeons rules would be quite poetic!

I think the most viable options would be for Bruce himself to write a Gazetteer-like book, probably for as a generic OGL supplement (i.e., one playable with any d20 game) or for OSRIC or another retro-clone, like BigMac suggests, or even for multiple systems (think e.g. to Wolfgang Baur's Midgard setting, which he published for both Pathfinder and AGE).
Note that the OGL does allow TPP to publish settings rather than full games -- actually, that was the hope of WotC, and full games were a (partly unintended, likely) side-effect. "Product Identity" is essentially the setting, whereas "OGL Content" are generally the rules (although publishers are free to do as they wish).